Rotary piston for a rotary internal combustion engine

ABSTRACT

The rotor for a rotary internal combustion engine has in each of its flank portions an elongated recess or pocket which is substantially narrower in width than the rotor flank so as to define between the recess and the rotor side faces two relatively large land portions in the flank surface. A plurality of ribs are circumferentially spaced with respect to the hub portion and radially extending between and interconnecting the flank surfaces along the sides and bottom walls of the pockets and the hub portion to thereby define a plurality of axially extending cooling fluid passageways adjacent the sides and bottom walls of each of the pockets. The bottom wall of each pocket has an extension integrally formed with said bottom wall and projecting axially from one side thereof to a point beyond the end of the surface of the hub portion adjacent said side of the bottom wall and which extension serves as a baffle for directing cooling fluid into said fluid passages.

United States Patent [1 1 Hermes et al.

[4 1 Nov. 12, 1974 l54l ROTARY PISTON FOR A ROTARY INTERNAL COMBUSTIONENGINE [75] Inventors: Walter L. Hermes, Cedar Grove;

' Howard R. Corwin, North Caldwell; Murray Berkowitz, Woodcliff Lake;Harold D. Lamping, Oakland, all of NJ.

[73] Assignee: Curtiss-Wright Corporation,

Wood-Ridge, NJ.

22 Filed: Dec. 26, 1973 2! Appl. No.: 428,109

Related US. Application Data [63] Continuation of Ser. No. 253,319, May15, 1972,

abandoned.

[56] References Cited UNITED STATES PATENTS 3,253,580 5/1966 Eberhard eta1, 123/8 FOREIGN PATENTS OR APPLICATIONS Germany 418/91 PrimaryExaminer-Charles J. Myhre Assistant ExaminerW. Rutledge, Jr. Attorney,Agent, or Firm-Arthur Frederick 57 ABSTRACT The rotor for a rotaryinternal combustion engine has in each of its flank portions anelongated recess or pocket which is substantially narrower in width thanthe rotor flank so as to define between the recess and the rotor sidefaces two relatively large land portions in the flank surface. Aplurality of ribs are circumferentially spaced with respect to the hubportion and radially extending between and interconnecting the flanksurfaces along the sides and bottom walls of the pockets and the hubportion to thereby define a plurality of axially extending cooling fluidpassageways adjacent the sides and bottom walls of each of the pockets.The bottom wall of each pocket has an extension integrally formed withsaid bottom wall and projecting axially from one side thereof to a pointbeyond the end of the surface of the hub portion adjacent said side ofthe bottom wall and which extension serves as a baffle for directingcooling fluid into said fluid passages,

3 Claims, 10 Drawing Figures AXIAL VELOCITY COMPONENT HXIRL VELOCITYCOMPONENT INTO OUT OF ROTOR POCKET PATENTEI] NOV 1 2 I974 ROTOR POCKETIN FEET PER SECOND IN FEET PER SECOND SIEEI 30$ 5 NARROW POCKET 5THNDQRDPOCKET BTC 50 50 IO TDC I0 50 50 ATC l I BEFORE TOP CENTER IN DEGREESHFTER TOP CENTER IN DEGREES 'i AIENIEuNuv 12 1314 3.847351 7 BACKGROUNDOF THE INVENTION With the necessity for reducing air pollution it hasbecome more and more essential to produce internal combustion engines ofincreased fuel combustion efficiency to minimize harmful exhaustemissions. Considerable effort has been exerted to increase the fuelburning efficiency of rotary piston engines of the Wankel type bymodifications in rotor design as is exemplified in the following U.S.Pats:

Froede et al. No. 3,097,632 Turner No. 3,359,955 Bentele No. 3,359,956Jones No. 3,405.695 Yamamoto No. 3,584,607 Hamada et al. No. 3,606,602Hejj No. 3,610,209 Hamada No. 3,249,095 Liebel No. 3,292,600 Meurer No.3,244,!59

It has been found that there is a direct correlationship between thecompleteness of fuel combustion and the degree of intimate mixingachieved between the fuel and air. Therefore, increased turbulencewithin the combustion chamber can be expected to increase theintermixing of fuel and air, and hence result in more completecombustion of fuel. It is particularly difficult I to achieve optimumfuel combustion in rotary piston engines of the Wankel type having acombustion system consisting of unthrottled air intake and controlledfuel injection into the combustion chamber adjacent an ignition device,such stratified charge fuel combustion systems being disclosed in theU.S. Pats. to Bentele, N0. 3,246,636 and Jones No. 3,393,667. In suchstratified charge systems, the larger the volumetric size of the workingchamber and/or the greater the speed of rotor rotation the moredifficult it is to provide substantially complete combustion of fuel.Thus, the proper stoichiometric mixing of fuel and air within the veryshort period of time available after fuel injection commences isdependent upon the establishment of a high degree of turbulence withinthe combustion chamber.

Accordingly, it is an object of this invention to provide in a rotarypiston, internal combustion engine, an improved rotor which is capableof producing high turbulence within the combustion chamber to therebyachieve intimate mixing of fuel and air and substantially completecombustion of fuel.

Another object of the present invention is to provide in a rotarypiston, internal combustion engine, an improved rotor which creates highgaseous fluid velocities within the working chamber to thereby provide aproper stoichiometric mixing of air and fuel and the efficientcombustion of the fuel.

SUMMARY OF THE INVENTION Now, therefore, the present inventioncontemplates,

in a rotary piston engine of the Wankel type, an improved rotor whichcoacts with the engine housing to provide within the combustion chambera high degree of turbulence to obtain improved mixing of air and fueland hence substantially complete combustion of the latter.

The rotor according to this invention comprises in each peripheralsurface or flank thereof a recess of pocket which is relatively long,narrow and deep in configuration. The pocket is dimensioned in width andpositioned so that a relatively wide flank surface portion of flank landextends on opposite sides of the pocket. These two flank lands coactwith the walls, defining the engine cavity within which the rotorrotates, to compress the gaseous fluid (air and fuel) in the combustionchamber and impart to the gaseous fluid a high velocity in a directionaxially toward and away from the pocket. With the gaseous fluidcascading into and out of the pocket at high velocity, a high turbulenceis cre ated within the pocket thereby rapidly effecting intimate mixingof fuel and air.

Preferably, each pocket in each flank is of generally rectangularconfiguration extending substantially the length of the rotor flank andlocated substantially midway between the opposite side faces of therotor. The pocket is also preferably constructed in width to be slightlygreater than one-third the dimensional width of the rotor flank so as toprovide the relatively large land portions on opposite sides of thepocket. I

The depth of each pocket is determined by the volumetric size that thepocket must be to achieve a desired compression ratio and, of course,taking into account the structural strength requirements of the rotor toresist the thermal and mechanical stresses to which it is subjected.Also, the rotor provides separation of the hub from the flank so as toprovide axially extending, cooling fluid flow passageways between thebottom wall of the pocket and the hub of the rotor to cooland pocketwalls, the hub and flank being connected by radial ribs coextensive withthe stiffening ribs.

In one embodiment of this invention the depth of the pocket is optimizedrelative to the strength requirements and the designed compression ratioby tapering the pocket side walls inwardly toward each other to thusprovide stiffening ribs interconnecting the hub with the rotor sidewalls of a size necessary to achieve the desired structural strength.

In another embodiment, the narrow pocket includes two shallow groovesextending from opposite sides of the leading portion of the pocket andbeyond the pocket toward the leading apex portion of the piston. Thesegrooves function todefine with the peripheral inner housing surfaceshooting passages or channels for directing high velocity streams offuel and air into the expansion combustion chamber.

BRIEF DESCRIPTION OF THE DRAWINGS The above and other objectives andadvantages of the present invention will appear more fully hereinafterfrom a consideration of the detailed description which follows whentaken together with the accompanying drawings wherein three embodimentsof the invention are illustrated and in which;

FIG. 1 is a side elevational view of a rotary piston engine having arotor according to this invention with parts broken away forillustration purposes only;

FIG. 2 is a plan view of the rotor shown in FIG. 1 showing one of theflank portions of the rotor;

FIG. 3 is a view in crosssection taken along line 3-3 of FIG. 2;

FIG. 4 is a cross-sectional view taken along line 44 of FIG. 2;

FIG. 5 is a fragmentary plan view of the rotor having the fuel injectionspray impingement pattern shown thereon;

FIG. 6 is a graph showing the axially directed velocities induced in theworking chamber by a rotor according to this invention as compared witha standard rotor;

DESCRIPTION OF PREFERRED EMBODIMENTS Now referring to the drawings andmore particularly to FIGS. 1 to 6, 10 generally designates a rotarypiston or rotor for a rotary piston internal combustion engine of theWankel type, such as disclosed in the US. Pat. No. 2,988,065 to Wankelet al and No. 3,246,636 to Bentele. As is conventional in such engines,the rotor 10 has a body portion having opposite side faces 12, a hubportion 14 and a periphery consisting of a plurality of flanks 16. Eachof the flanks 16 has a slightly curved surface extending between theapex seals 18 disposed in the apex portions of the rotary piston. Therotary piston is mounted on an eccentric portion 11 of a shaft 13 forrotation within a cavity formed by the engine housing 15. The cavity ispartially defined by an inner trochoidal shaped peripheral wall 20. Theperipheral surface 20 may have a multi-lobe profile and, preferably, isan epitrochoid having one less lobe than the number of flanks 16 ofrotor 10. Suitable intake and exhaust ports 21 and 23 are provided inthe housing 15 to pass air or air and fuel mixture into the combustionchamber formed by the cavity walls'and the flanks and exhaust spentproducts of combustion from the combustion I chambers. In a stratifiedcharge fuel combustion system, as exemplified in the US. Pats. toBentele, No. 3,246,636 and Jones, No. 3,393,667, the fuel is introducedinto the combustion chambers by a fuel injector 17 (see FIG. 1) foradmixture with air.

In accordance with this invention, rotor 10 has in each flank 16, anelongated, narrow and relatively deep recess 22. The recess 22 ispreferably rectangular in shape, when viewed in plan as shown in FIG. 2,with a length less than the length of the flank between adjacent apexseals 18 and with a width substantially less than the width of flanks 16between opposite side faces 12. As illustrated, the recess width may beaboutone third the width of flank 16. The recess 22 is preferablylocated in flank 16 midway between side faces 12 and in slightly closerspaced relation to the trailing apex seal 18 than the space between therecess and the leading apex seal 18 relative to the direction ofrotation as shown by arrow A. The recess 22 forms in flank 16 tworelatively wide land portions 24 on opposite sides of the recess.

As best shown in FIGS. I, 3 and 4, recess 22 is defined by two spaced,parallel walls 26 and 28 and a flat bottom wall 30 which, as viewed inFIG. 1, is slightly inclined at the opposite ends 32 outwardly towardand into merger with the flank surface. The walls 26 and 28 extendperpendicularly to the surface of flanks 22 and bottom wall 30. As bestshown in FIG. 3, side faces 12 and flanks 22 are interconnected byintegrally formed, radially extending stiffening ribs 25. The depth ofrecess 22 is not critical and is only a function of its dimensionalwidth and the compression ratio desired. In other words, the smaller thewidth of recess 22 the greater the depth to retain the same compressionratio.

In operation of rotor 10 and its rotation within the housing cavityrelative to trochoidal surface 20, the air or mixture of fuel and air iscompressed or squeezed between flank surface 16 and trochoidal surface20. This compression of the fluid in the combustion chamber imparts tothe fluid an axially directed velocity inwardly toward and outwardly ofthe recess. These axially directed velocities vary as rotor 10approaches and passes top dead center (represented by the line B in FIG.1 as is graphically illustrated in FIG. 6. As shown in the graph of FIG.6, the relatively wide land portions 24 provide at 6,000 RPM axiallydirected velocities of high magnitude as compared with a rotary pistonhaving a standard recess or pocket which is of relatively wide, shallowconfiguration such as the type shown in the US. Pat. to Bentele, No.3,359,956 and Lamm et al. No. 3,398,724. Thesev high axial velocitycomponents produce a high degree of turbulence in the combustion chamberand hence improved intermixing of fuel and air and more complete fuelcombustion.

As best shown in FIG. 3, the flanks 16, including the walls 26, 28 and30 are radially separated from hub 14 and interconnected bycircumferentially spaced radially extending ribs 27, the ribs 27 beingcoextensive with stiffening ribs 25. The bottom wall 30 and hub 14define between ribs 27 a plurality of axial cooling fluid flowpassageways 29 through which a cooling fluid, such as oil, can flow tocool the walls 26, 28 and 30 of pocket 22 and thereby preventdeterioration of the rotor flanks due to excessive heating. The additionof passageways 29 to the rotor provides ribs 27 with flexibility whichcompensates for the thermal growth of rotor 10 without distortion of thebearing seat in hub portion 14 of the rotor. To better direct coolingfluid flow into passageways 29, bottom wall 30 is provided with annularextensions 31 which project axially beyond the plane containing the endsurfaces 33 of hub 14.

This improved fuel combustion is particularly evident when rotary piston10 is employed in conjunction with a Stratified charge type of fuelcombustion system wherein fuel is injected into air trapped in thecombustion chamber by a fuel injector 17 which emits fuel in a pluralityof streams past an ignition means, such as a spark plug 19. Particularlyexcellent results were achieved when fuel was injected so as to form theimpingement patterns 36 shown in FIG. 5. This fuel spray patterntogether with the high turbulence in the combustion chamber providesintimate fuel mixing and vaporization of fuel and, hence efficient fuelcombustion. The best high power combustion efficiency has been achievedby using a multi-stream fuel injector spray pattern wherein some of thefuel streams are directed counter to the direction of the rotorrotation. The position of pocket 22 in flank surface 14 closer to thetrailing" apex 18 than the leading" apex 18 was selected in relation tofuel injection and ignition to minimize the amount of air passing aheadof the initiation of fuel injection and to provide for completelypainting" the surface of pocket 22 and land portions 24 with fuel andthereby obtain intimate mixing of fuel and air inside the pocket to thusachieve optimum fuel combustion.

In FIGS. 7 and 8 is shown a second embodiment of this invention whereinincreased structural strength is achieved over rotor I0 shown in FIGS. 1to 6. The rotor 40 of this second embodiment functions to provide thesame high magnitude of axial velocities as rotor 10 and therefore has anelongated, narrow pocket or recess in each of the flanks of the rotor.Like parts of rotor 40 corresponding to the parts of rotor 10 will bedesignated by the same reference number but with the suffix A addedthereto.

As illustrated in FIGS. 7 and 8, rotor 40 has a narrow pocket or recess22A in each flank 16A of the rotary piston. The recess 22A isessentially the same as recess 22 except that side walls 26A and 28A ofrecess 22A have lower portions 42 which incline toward each other in adirection toward bottom wall 30A. As best shown in FIG. 7, the hubportion .14A is connectedto flanks I the lower portions 42 of recessside walls 26A and 28A than if side walls were straight as in rotor 10(see FIG. 3) or as shown by the phantom lines 48 in FIG. 7. Thus, withthicker ribs 48, rotor has greater structural strength to resist thethermal and mechanical stresses imposed on the rotary piston. Of course,as compared with recess 22, recess 22A will have to be slightly greaterin width than the width of recess 22 to permit rotor 40 to achieve thesame compression ratios as obtained by rotor 10.

In FIG. 9 is shown a third embodiment of the present invention whichcomprises a rotor 50 having in each flank surface a pocket or recess 22Bdiffering from the pocket or recess 22A of rotor 40 shown in FIGS. 7 and8 in that the pocket 228 includes two relatively shallow, taperinggrooves 52. The grooves 52 extend on opposite sides of the leadingportion of the pocket and forwardly of the latter toward the leading endof flank surfaces 16 relative to the direction of rotor rotation. Inview of the close similarity of rotor 50 to pis-.

tons l0 and 40, parts of rotor 50 corresponding to like parts of pistons10 and 40 have been designated by the same number but with the suffix Badded thereto.

As shown in FIG. 9, each groove 52 is preferably arcuate shaped incross-section and taper forwardly to a point where is merges with theflank surface 168.

It has been found that in order to improve fuel consumption at highpower output in an engine having a stratifled charge type fuelcombustion system and rotors l0 and 40, there must be increasedutilization of the air within the combustion chamber for fuelcombustion. This increased utilization of air for burning fuel whichotherwise would be unburned is attained by use of rotor 50 because ofgrooves 52 which form with the inner peripheral surface of the housing(not shown), similar to peripheral surface 20 (FIG. l),

shooting channels or passages. These shooting.

channels conduct presurrized fuel and some air at high velocity into thefuel starved, expansion combustion chamber (space to the right of thelobe shown in FIG. 1) in advance of the compression-combustion chamber(space to the left of the lobe shown in FIG. 1) relative to thedirection of piston rotation A. These two high velocity fluid streamsinjected by grooves 52 into the expansion working chamber accomplishes,in effect, a recovery of air which has passed into the expansion chamberbefore fuel injection by causing the air to mix with the fuel and,hence, cause the latter to burn. which fuel would otherwise remainunburned for lack of air and/or sufficient time to mix with air in thecompression-combustion chamber.

It is believed now readily apparent that the present invention providesa rotor for a rotary piston internal combustion engine which coacts withthe engine housing to provide improved turbulence within the combustionchamber and, hence, rapid and intimate mixing of fuel and air foroptimum combustion of the fuel.

Although but three embodiments of the invention have been illustratedand described in detail, it is to be understood that the invention isnot limited thereto. Various changes can be made in the arrangement ofparts without departing from the spirit and scope of the invention asthe same will now be understood by those skilled in the art.

What is claimed is:

l. A rotor for a rotary piston, internal combustion engine comprising:

a. a body portion having a hub portion, opposite side faces and aplurality of contiguous flank surfaces spaced radially outward of thehub portion;

b. said hub portion having opposite end surfaces each of which lie in aplane axially and inwardly spaced from the plane of the associated sideface;

c. a pocket in each of the flank surfaces;

d. each of said pockets being generally rectangular in shape and havingopposite side walls and a bottom wall;

e. a plurality of ribs circumferentially spaced with respect to the hubportion and radially extending between and interconnecting the flanksurfaces along the sides and bottom walls of the pockets and the hubportion;

f; said ribs defining with the hub portion and the flank surfaces aplurality of axially extending cooling fluid flow passageways adjacentthe side and bottom walls of each of the pockets; and

g. the bottom wall of each pocket has an extension integrally formedwith said bottom wall and projecting axially from one side thereof to apoint beyond a radial plane containing the end surface of the hubportion adjacent said side of the bottom wall and which extension servesas a baffle for directing cooling fluid into said fluid passageways.

2. The apparatus of claim 1 wherein the bottom wall .of each pocket hasa second integral extension which projects axially from the oppositeside of the bottom wall from said first extension and extends beyond theradial plane containing the opposite end surface of the hub portion todirect cooling fluid flow relative to said fluid passageways.

3. A rotor for a rotary piston internal combustion engine comprising:

a. a body portion having a hub portion, side faces and a plurality ofcontiguous flank surfaces spaced radially outward of said hub portion;

h. each of said end surface of the hub portion being in a plane axiallyinwardly spaced from the plane of the associated side face;

c. a pocket in each of said flank surfaces;

d. each of said pockets having an elongated configu ration and a widthsubstantially less than the total width of the associated flank surfaceextending between said opposite side faces so as to form two relativelywide land portions of the flank surfaces on the opposite sides of thepocket;

e. each of said pockets being of generally rectangular shape and havingopposite side walls and bottom wall; f. a plurality of ribscircumferentially spaced with respect to the hub portion and radiallyextending between and interconnecting the flank surfaces along the sideand bottom walls of the pockets and the hub portion;

g. said ribs defining with the hub portion and the flank surfaces aplurality of axially extending cooling fluid passageways adjacent theside and bottom walls of each of the pockets; and

h. extension portions formed integrally with the bottom walls of each ofsaid pockets and projecting axially from opposite sides of the bottomwall to points beyond radial planes containing the end surfaces of thehub portion adjacent said opposite sides of the bottom wall to directcooling fluid into and from said fluid passageways.

1. A rotor for a rotary piston, internal combustion engine comprising:a. a body poRtion having a hub portion, opposite side faces and aplurality of contiguous flank surfaces spaced radially outward of thehub portion; b. said hub portion having opposite end surfaces each ofwhich lie in a plane axially and inwardly spaced from the plane of theassociated side face; c. a pocket in each of the flank surfaces; d. eachof said pockets being generally rectangular in shape and having oppositeside walls and a bottom wall; e. a plurality of ribs circumferentiallyspaced with respect to the hub portion and radially extending betweenand interconnecting the flank surfaces along the sides and bottom wallsof the pockets and the hub portion; f. said ribs defining with the hubportion and the flank surfaces a plurality of axially extending coolingfluid flow passageways adjacent the side and bottom walls of each of thepockets; and g. the bottom wall of each pocket has an extensionintegrally formed with said bottom wall and projecting axially from oneside thereof to a point beyond a radial plane containing the end surfaceof the hub portion adjacent said side of the bottom wall and whichextension serves as a baffle for directing cooling fluid into said fluidpassageways.
 2. The apparatus of claim 1 wherein the bottom wall of eachpocket has a second integral extension which projects axially from theopposite side of the bottom wall from said first extension and extendsbeyond the radial plane containing the opposite end surface of the hubportion to direct cooling fluid flow relative to said fluid passageways.3. A rotor for a rotary piston internal combustion engine comprising: a.a body portion having a hub portion, side faces and a plurality ofcontiguous flank surfaces spaced radially outward of said hub portion;b. each of said end surface of the hub portion being in a plane axiallyinwardly spaced from the plane of the associated side face; c. a pocketin each of said flank surfaces; d. each of said pockets having anelongated configuration and a width substantially less than the totalwidth of the associated flank surface extending between said oppositeside faces so as to form two relatively wide land portions of the flanksurfaces on the opposite sides of the pocket; e. each of said pocketsbeing of generally rectangular shape and having opposite side walls andbottom wall; f. a plurality of ribs circumferentially spaced withrespect to the hub portion and radially extending between andinterconnecting the flank surfaces along the side and bottom walls ofthe pockets and the hub portion; g. said ribs defining with the hubportion and the flank surfaces a plurality of axially extending coolingfluid passageways adjacent the side and bottom walls of each of thepockets; and h. extension portions formed integrally with the bottomwalls of each of said pockets and projecting axially from opposite sidesof the bottom wall to points beyond radial planes containing the endsurfaces of the hub portion adjacent said opposite sides of the bottomwall to direct cooling fluid into and from said fluid passageways.